Polymeric epoxy resins have been known for a long time. As a general rule they are prepared by reacting polyepoxides having on average at least two terminal or lateral epoxide groups per molecule with hardeners, more particularly aminic hardeners, which are diamines or polyamines. These polymeric epoxy resins have diverse fields of application, predominantly their use as paints and coating materials (e.g., application of a topcoat to a substrate).
EP-A-1,518,875 describes special hardeners for water-based epoxy resin systems, these hardeners being obtainable by reacting a mixture of (a) at least one epoxidized polyalkylene oxide, selected from the group consisting of epoxidized polyethylene oxides, epoxidized polypropylene oxides, and polyethylene-propylene oxides, (b) at least one epoxidized aromatic hydroxy compound selected from the group consisting of bisphenol A epoxides and bisphenol F epoxides, and (c) at least one aromatic hydroxy compound selected from the group consisting of bisphenol A and bisphenol F to give an intermediate and subsequently reacting this intermediate with a polyamine. Also disclosed is the use of these hardeners for producing transparent varnishes and coating materials (application of a topcoat to a substrate, for floor coatings, for example).
Porous absorbents have long been known in their capacity as sound-damping materials. This effect is based on absorption of the sound waves in the open-cell pore structure, and conversion of the sound energy into heat energy. Conventional porous absorbents are more effective and more broad-spectrum in their effect as the frequency increases, and therefore are more often used for damping moderate to relative high frequencies. The sound-damping effect is expressed by the sound absorption coefficient (α0), which is determined by measurement in an impedance tube (Kund tube) in accordance with ISO 10534. Here, a value of 1.0 denotes that all of the sound waves are absorbed at the frequency in question; a value of 0.5 corresponds, accordingly, to a reduction in the sound level of the frequency in question by half.